Heat riser continued

[Dave _S]

Hey, I installed a new heat riser on my rig. My question is how much is the counterweight supposed to move when the engine is hot? I had the impression that as the engine warmed up the valve would progressively open until the counterweight had moved 90 degrees (full open with engine hot). Mine opens maybe 20 degrees with the engine hot. The counterweight moves freely, it just doesn't seem to open much when hot. Is this normal for a bi-metallic spring type heat riser?

Thanks,
Dave

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1977 WT Cherokee, 401V8, TH400, PT Quadra-trac.

[Snakeyes_Tx]

Youre talking about the flap on the passenger side exhaust manifold right? I'm just tryin to make sure. That thing opens via the compression of he motor. When my motor runs at about 1000 rpm idle, the valve is halfway open. As I hit the gas, it blows wide open. Of course I don't have the stove pipe or the part it connects to, but I needed to keep the valve to make up that space between the Y-pipe and the manifold.

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http://www.virtue.nu/yazahx/rand/sig.jpg

Snakeyes_Tx
86 J-20 "The Rusty Dinosaur"
360/727/208/44HD/60 <- 2nd of all of them.
"If you don't know what the numbers mean, you don't need to be here!"

[Dave _S]

Snakeyes, you are right the heat riser seems to just blow open as I open the throttle. It will blow open even with the engine cold. I guess the thermostatic spring just applies more force when cold than hot, but not enough to keep the valve shut when you mash the throttle. Anyway, this does appear to be the way its designed to work and since the valve is new, and the engine runs fine, I am not about to unbolt the head pipes again. I am going to assume its working the way its supposed to.

The description of how its supposed to work in the Haynes manual is apparently misleading. According to Haynes the valve is closed when cold, and opens when hot. Not so. The valve is pretty much always closed. Its just blows open more easily when the engine is hot.

Well, now maybe I will finally be able to get the *$%&$#* choke to work.

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1977 WT Cherokee, 401V8, TH400, PT Quadra-trac.

[gbarrett]

Ooooooops! When I replaced the exhaust manifold gaskets, I took that piece off and drilled out the shaft and welded the holes on the side closed. I found that it contributed nothing to the overall function of my engine, of course I live in SW Florida - home of the eternal summer.

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84 GW
Driveline is
Stock 360/727 combo.
New paint, carpet, stereo. Rhino grille, etc.
http://home.earthlink.net/~getoverit/index.html

[Snakeyes_Tx]

I was always under the impression that the valve just opened via exhaust pressure, not heat. Mine blows almost completely open from cold to hot. It doesn't make a difference on my rig. At one point, I wanted to wire the flap wide open, but noticed that the exhaust pressure does that for me already.

If it runs fine, I wouldn't worry about it though.

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http://www.virtue.nu/yazahx/rand/sig.jpg

Snakeyes_Tx
86 J-20 "The Rusty Dinosaur"
360/727/208/44HD/60 <- 2nd of all of them.
"If you don't know what the numbers mean, you don't need to be here!"